Process of producing cooking utensils



INVENI'OR ATTORNEY HIS Jan. 3, 1961 A. c. SCAVULLO PROCESS OF PRODUCINGCOOKING UTENSILS Original Filed June 15, 1954 N 0 "wm w v Q m K "\m u 42 S a f a m m n m F m m y "\m n a a W A B 5 w 0 O I H m o 7 I F 2 I 6 F2 United States Patent PROCESS OF PRODUCING COOKING UTENSILS Angelo C.Scavullo, Jamaica, N.Y., assignor to Legion Utensils Co., Inc., acorporation of New York Original application June 15, 1954, Ser. No.436,915. Divided and this application Sept. 10, 1958, Ser. No. 760,250

1 Claim. (Cl. 2042'5) My application for patent is a division of mycopending U.S. application Ser. No. 436,915, filed June 15, 1954, andnow abandoned, entitled Cooking Utensil and Method, and the inventionrelates to cooking utensils and vessels which provide superior heatconductivity and resistance to corrosion. As well, it relates to amethod and apparatus for making such utensils and vessels.

An object of my invention is to provide an inexpensive :and highlydurable utensil which can be manufactured :in a minimum number ofoperations with the elimination of any scams or welts on the finishedproduct and with .a high heat conductivity so that applied heat willevenly \distribute throughout the utensil so as to eliminate scorchingof food, due to local hot spots, and provide uniform heating of the foodbeing cooked therein.

Another object is to produce a cooking vessel with exrceptionalresistance to corrosion by the acids, bases and salts of foodstuffsbeing cooked therein and whose surfaces may be easily cleaned, which,while presenting an attractive and pleasing appearance, is impervious tothe foods, and which will eliminate the contamination of foods cookedtherein by the previously cooked foods.

A further object of my invention is to provide a simple, direct,efficient and economical method and apparatus for making such a utensil.

Other objects and advantages, in part, will be obvious and in partpointed out hereinafter during the course of the following description.

My invention accordingly resides in the features of construction,combination of elements, and arrangements of parts and in the severalsteps and the relation of each of the same with one or more of theothers, the scope of the application of all of which will be more fullyset forth in the claim at the end of this specification.

In the accompanying drawings:

Fig. l is a side view of the composite metal sheet used in my invention;

Fig. 2 is a cross-sectional view of my utensil deep- (lrawn from thesheet of Fig. 1;

Fig. 3 is a representation of the apparatus employed to carry out onestep of forming my utensil;

Fig. 4 is a cross-sectional view of the utensil of Fig. 2 after thecopper-plating of a portion;

Fig. 5 shows the method'of attaching a handle to the utensil; and

Fig. 6 is a cross-sectional view of the final form of my invention,showing the handle attached.

Like reference characters refer to like parts throughout the severalviews of the drawing.

As conducive to a clearer understanding of certain features of myinvention, it may be noted at this point that stainless steels, as forexample the austenitic chromium-nickel stainless steels and especiallythose containing to 25% chromium and 7% to nickel and the remaindersubstantially all iron, with as low a carbon content as commerciallypossible, have come into widespread use as a material for theconstruction of cooking utensils to the other portions of the pan, butremains concentrated in the one portion. Localized hot spots arecreated. As a consequence, food on those portions will be burned andfood in other portions will not be cooked, unless the mass of food iscontinually stirred.

It has been proposed to overcome the heat distribution problem by makinga utensil of stainless steel on the inside and thick copper on theoutside, as copper possesses excellent heat conductive characteristics.Utensils of this character, having the two metals tightly fittedtogether and spot-welded, were not satisfactory because of cracksforming between the metals permitting the entrance of water andresultant warping and blistering of the metal. Likewise, stainless steelutensils with an electroplated copper coating on all the outsidesurfaces of the utensil, with a subsequent build-up of theelectrodeposited layer by means of spraying on hot copper, were notentirely satisfactory because of warping.

In the prior art it also has been proposed to limit the amount of copperemployed on solid stainless steel utensils by depositing a layer ofcopper on the bottom and on a portion around the sides a short distancefrom the bottom leaving the stainless steel surface on the major portionof the utensil sides. This arrangement permits proper distribution ofheat throughout the copper-plated portion, but leaves improper andunequal heating effects in the unplated portion.

In another approach to the problem, the use of copper is entirelyavoided and the vessel is constructed entirely from a composite metalsheet comprising a layer of stainless steel on the top and bottom of thesheet with a layer of mild steel in between the two. With thisconstruction the stainless steel layers offer corrosion resistance whilethe core of mild steel olfers heat distribution. This construction,however, leaves much to be desired in the matter of uniform cooking.

Accordingly, the object of my invention is the production of a cookingutensil that is of low cost with exceptional durability andwear-resistance properties and excellent heat distributioncharacteristics, while at the same time presenting an attractiveappearance for the necessary consumer acceptance.

Referring now more particularly to the practice of my invention, Iproduce a cooking utensil from composite metal sheet which is rolledfrom stacked sheets composed of two stainless steel layers, preferablywhat is known as 18-8 chrome-nickel stainless steel, with an internalmild steel layer. The composite sheet is deep-drawn to inexpensivelyproduce deep-drawn vessels of the desired configuration.

In the drawn form, therefore, the vessel comprises inner and iOUtEIlayers of stainless steel. 4

I now cut a shallow V-shaped groove into the arcuate portion at theoutside bottom edge of the partially formed vessel to sharply define theareas of bottom and side-Wall.

The bottom area now is processed to further improve the heat-conductingcharacteristics of the vessel as a whole. Copper is electrodeposited onthe bottom of the vessel and on the bottom edge of the shallow V-shapedgroove. A balanced heat conductivity between bottom and side-walls isthereby provided at reasonable cost; the copper utilized is a relativelysmall amount.

As specifically illustrative of the practice of my invention, I employcomposite sheet metal, shown in Fig. l, which consists of three layersof steel rolled into an overlying relationship. The top and bottomlayers 10 are of stainless steel, preferably of the type known to thetrade as 18-8, a composition of 18% chromium, 8% nickel and theremainder low-carbon iron. And the intermediate layer 11 is of mildsteel. Each of the outer layers is substantially thinner than theintermediate layer of mild low-carbon steel. Actually, best results arehad where the thickness of the intermediate layer amounts .to some 1 /2to times the total thickness of the inner and outer layers. The figureis critical because with lesser thicknesses of mild steel there isinadequate heat-distribution and, with greater thicknessses, warping isencountered.

In making my utensil the tri-ply sheet is purchased from the mill insizes and thicknesses desired. It will be noted, at this point, thatsome variation in the gauge of the material used can be utilized as itmay be desired that the utensil be of the heavy duty type with a thickergauge such as that used in hotels and the like, or possibly for thedomestic customer where a light, convenient utensil of a lighter gaugeis desired. In a preferred form of my invention the proportions of thelayers, regardless of the gauge, are 20% of the total thickness in eachof stainless steel layers and 60% in the mild steel layer.

After being cut to size the sheet material is deep-drawn to provide aroughly formed cooking utensil of the desired configuration. By thisoperation a utensil body is produced free of seams or welts where dirtor cleaning compounds might lodge or leaks might start. One type ofdeep-drawn utensil body is shown in Fig. 2. The utensil has inside andoutside layers of stainless steel 10-10, and an internal layer 11 ofmild steel throughout the bo y- I now cuta shallow peripheral .V-shapedgroove 12 in the vessel outer surface as shown in Fig. 4 along thearcuate portion of the vessel which constitutes the outside bottom edge.The groove is preferably machined on a line which is generally above thecenter of the arcuate portion on its outer surface 10 and below thestart of the straight side-wall portion. This groove defines the upperextremity of .a portion of the vessel to which copper is to bedeposited, as will be explained hereinafter.

I roughen the entire bottom of the outside surface 10 of the vesselbelow groove 12 by grinding or abrading on machines or belt. The abradedsurface is then pas.- sivated by immersion in a bath of sulphuric acid.In this manner the surface is prepared for electroplating I now coat theoutside surface of the vessel above groove 12 with a beeswax or asimilar substance to prevent the depositing of copper thereon. Thispractice leaves exposed for electroplating that area in which I findthat the highest amount of heat conductivity is required.

The vessel is put into position for electroplating in tank 24, eitherstill plating or plating wherein the vessel is slowly rotated in theplating bath. For plating with rotation of the work a copper bar 13 issecured to the inside of the vessel as at points 14 to establish goodelectrical contact, the bar in turn being mechanically and electricallyconnected to a copper shaft 15 which is adapted to be rotated by somesuitable means not indicated in the drawing.

Shaft 15 is electrically connected by way of a copper spring contactbrush 16 and lead 17 to the negative terminal of a source of directcurrent electrical energy such as a storage cell 18. And the positiveterminal of the source 18 is connected by lead 19 to a metallic rod 29which is secured in a position near the inside tip edge of the tank 24,but insulated therefrom.

Copper bars or plates 22 suspended from the rod 20 on metallic hooks 21in my plate apertures provide an electrical connection between the rod2t and the plates 22, the latter forming the anodes of an electrolyticcell. A suitable electrolyte 23 is contained in the tank 24 at a levelhigh enough to completely submerge the portion of the vessel that isdesired to be plated. This electrolyte is preferably a copper sulphatesolution containing a small amount of sulphuric acid, but othersolutions may be used. .By virtue of theconnection to thenegativeterminal of the source 18 the vessel forms the cathode of theelectrolytic cell.

In the plating operation, after all the connections are made, the vesselis rotated at the desired speed by the shaft 15. Preferably the rotationis such as to give the periphery of the vessel a linear velocity ofabout 6 feet per minute. Due to the electrolyte action copper isdeposited on the outer surface of the stainless steel bottom belowgnoove 12 which is not protected by the beeswax coating. Theelectroplating operation is continued until it builds up a layer ofcopper 9, as shown in Fig. 4, of desired thickness.

The method of electroplating described herein is characterized byextreme simplicity in the apparatus required and in operation. Thecopper coating deposited on the vessel is of uniform thickness except ona portion of the bottom edge 7, as shown in Fig. 4, where it isdesirably thicker. This thickened section serves the function ofthermally reinforcing the junction between the bottom and side walls. Asa result, better heat conduction is provided between the bottom of theutensil to which the heat is usually applied and the side-walls. Due tothe agitation of the electrolyte caused by rotation of the vessel, nogas bubbles are included in the copper coating which is deposited. Thecoating accordingly is dense and solid.

My rotating process ofelectroplating is used preferably due to itssuperior effect in the bonding of copper directly to stainless steel byeliminating the tendency of the oopper layer to blister in-use. However,the layer of copper may be applied as by still-plating where desired. Instill-platingl strike a thin layer of copper on the stationary utensilby utilizing a high current density at first amps. p.s.i. in the platingprocess and then reducing the current density to lower amount 50 amps.p.s.i.

Due to the time and current requirements for electrodepositing thecopper required, it may be preferred to build up the layer '9 to desiredthickness by spraying hot copper particles onto the utensil afterelectroplating the first copper coating. This step may be employed asdesired.

In addition to the improved heat distribution had throughout the utensilbody by means of the inner layer of mild steel, 1 find that additionaladvantages in heat conductivity are had with the copper layer 9. Thislayer gives added effectiveness to the heat distribution proper- "es ofthe utensil and greatly assists in evenly distributing heat around thecooking vessel in use, especially to prevent the formation of local hotspots on the bottom which might cause burning or scorching of the food,whether in liquid or solid form.

After the vessel has been plated it is then ready to have its handleattached. And referring now to Fig. 5, it will be seen that handle 25has a curved and flattened lower end 26. The handle preferably isfashioned of 18-8 chromium-nickel stainless steel, although other metalof comparatively poor heat conductivity characteristics may be used. Andin attaching it to the vessel its curved end 26 is held against theoutside wall of the vessel 8 at a convenient location as shown in Fig.5, and by means of a welding process, such as resistance or welding orspot-welding, is permanently secured thereto. The welded areas 27 areshown in Fig. 5. A handle attached in this manner is vastly superior inruggedness as compared to a handle which is riveted or attached in someother like manner. Rough and constant usage will not damage either theutensil or dislocate the handle and maintenance expense is eliminated.The long lasting qualities and durability of this utensil in its finalform are unexcellecl.

One of the major advantages of my utensil is the high- 1y efiicient andbalanced heat conductivity of the bottom and sidewalls which is had.Heat applied to the bottom is distributed over the whole bottom andside-walls with the tri-ply construction and the cooperating efliect ofthe .hQttom copper .layer. The food .in the .vessel there fore is heateduniformly. The increased thickness of copper at the junction between thebottom and sides of the vessel has been found desirable in order tobetter distribute the heat up the side walls from the bottom. Thethickened edge portion is also desirable because a substantial thicknessof copper remains on the edge after the vessel has been subjected towear caused by the rough handling encountered in actual practical use.

The cleaning of cooking utensils made with my invention is reduced to anabsolute minimum by providing the major portion of the utensil withstainless steel surfaces without sacrificing any of the excellentheat-conductivity properties. At the same time advantage is taken of theproperties of stainless steel that prevent corrosion in the cooking andserving of food. Moreover, my invention permits the use of a variationin the gauges of metal used to meet the wide range of demands of themarket in matters of size, type, Weight and cost. My invention isparticularly utilized in the production of utensils such as pots,kettles, casseroles, chafing dishes, steamers and the like.

A particular advantage of my utensil is its freedom from warping andblistering. The simple method of constructing my utensil eliminates allwarping. And blistering is avoided by the rotation of the vessel duringelectroplating which insures an even deposit of copper and removal ofgas bubbles from the vessel surface. As the copper layer is formed nogas is trapped between the copper and steel.

Thus it will be seen that in my invention there is had a utensil andmethod of producing the same in which the various objects hereinbeforeset forth together with my thoroughly practical advantages aresuccessfully achieved. It will be seen that the vessel is attractive,rugged and well adapted to handling in use, that it is calculated to befree of warping and blistering in use, and that it is designed to giveuniform heating through all parts. Also, it will be seen that my utensilis produced in a simple, direct and efficient manner.

As many possible embodiments may be made of my invention, and as manychanges may be made in the embodiment hereinbefore set forth, it is tobe understood that all matter herein, whether described or illustrated,is to be interpreted as illustrative and not as a limitation.

Having described my invention, I claim:

The process of forming a culinary vessel compressing deep-drawing thevessel out of a tri-ply composite sheet of a thick layer of mild lowcarbon steel sandwiched between two thin layers of l88 chromiumnickelstainless steel to the shape of the desired vessel to give side wallsand a bottom with 18-8 chromiumnickel stainless steel interior andexterior layers, cutting a shallow peripheral groove into said exterior18-8 chromium-nickel stainless steel layer at about the junction ofbottom and side walls, mechanically abrading and chemically passivatingthe surface beneath the groove, masking the side walls above said grooveagainst plating, and rotating the shaped vessel at a linear velocity ofabout 6 feet per minute in a copper electroplating bath wherein thevessel is made the cathode and a plurality of copper bars serve asanodes, whereby a layer of copper is deposited on the portion of theoutside surface in and below said groove while said vessel iscontinuously rotated to give a thickened bottom and thicker edge.

References Cited in the file of this patent UNITED STATES PATENTS733,630 Dana July 14, 1903 1,293,562 Siegel Feb. 4, 1919 2,358,104Scavullo Sept. 12, 1944 2,363,973 Kennedy et a1. Nov. 28, 1944 2,549,610Kennedy et a1. Apr. 17, 1951 2,560,966 Lee July 17, 1951

